In recent years, development of liquid crystal display devices has been robust. The majority of these liquid crystal display devices are equipped with an active matrix-driven liquid crystal display panel.
More specifically, such liquid crystal display panels typically include a device substrate and an opposite substrate arranged facing one another and a liquid crystal layer sandwiched between the device substrate and the opposite substrate. On the surface of the device substrate facing the liquid crystal layer, a plurality of pixel electrodes are arranged in a matrix pattern.
Moreover, on the surface of the device substrate or the opposite substrate facing the liquid crystal layer, a plurality of color filter layers containing coloring materials (pigment or dye) in colors such as red (R), green (G), or blue (B) are arranged in a repeating pattern. These color filter layers are formed in regions known as pixel regions that overlap with the respective pixel electrodes when viewed in a plan view.
In a liquid crystal display device equipped with a transmissive liquid crystal display panel, white illumination light emitted from a backlight enters the liquid crystal display panel from the device substrate side. Furthermore, red light, green light, and blue light are emitted from the opposite substrate side of the liquid crystal display panel, thereby making it possible to display color images.
In such liquid crystal display panels, while it appears as though the color filter layers color the white illumination light emitted from the backlight, in reality the color filter layers simply transmit only certain wavelength components of the light according to the coloring materials used and absorb the other wavelength components. For example, the red color filter layers transmit the red wavelength components of the illumination light and absorb the other green and blue wavelength components.
Therefore, in such liquid crystal display panels, only a relatively small amount of the illumination light emitted from the backlight is actually used to display images, with most of the light not being used and going to waste. The amount of light that a liquid crystal display panel transmits relative to the total amount of illumination light from the backlight that originally enters the liquid crystal display panel is generally known as transmittance. The liquid crystal display panels used in mobile phones, for example, typically have a transmittance on the order of a few percent. The reason the transmittance of liquid crystal display panels is so low is because of this large amount of light that is absorbed by the color filter layers and not transmitted.
Moreover, the fact that the transmittance of such liquid crystal display panels is so low also means that much of the electrical power consumed to illuminate the backlight goes to waste.
To make use of this light that is not used to display images and would otherwise be wasted, liquid crystal display devices in which the color filter layers are made using dye-sensitized solar cells that convert the light absorbed by the color filter layers to electrical power have been proposed (see Patent Document 1, for example).
In dye-sensitized solar cells, sensitizing dye adsorption layers formed by adsorbing a dye (a sensitizing dye) into the surfaces of titanium dioxide particles and an electrolyte layer containing iodine are arranged between a positive electrode and a negative electrode, for example. Irradiating the dye-sensitized solar cell with light creates an electromotive force between the positive electrode and the negative electrode.